1. Field of the Invention
This invention relates generally to systems for testing electrical and mechanical energy transfer systems that exhibit vibratory and other responses to electrical or mechanical input energy, and more particularly, to an arrangement that isolates a mechanical or electrical system under test and produces signals and data corresponding to a plurality of operating characteristics of the system under test in response to the input energy.
2. Description of the Related Art
Noise testing of gears to date has been attempted by methods that rigidly mount the gear or axle assemblies in one or more planes. Some other previous attempts chose to have one of the rigidly mounted planes resonate at a frequency sympathetic to gear noise. None of these methods, or any other rigidly mounted test system has been successful. This is due to the lack of repeatability of the previous systems, largely as a result of interacting resonances, and external background noise that is transferred through the rigid mounting system. This is especially true in a production test environment.
These deficiencies in the prior art are most evident in the axle industry. At this time, the only widely accepted way of measuring gear noise is to acquire an assembled axle and install it in a test car. A specially trained individual then drives the car over its typical operating range while carefully listening for axle gear noise. The individual rates the quality of axle gear noise on a scale that is typically 0 to 10. Ten is usually a perfect axle, i.e. one that has no gear noise. This method is made difficult by:
1 The lack of available trained noise rating individuals
2 The cost of test cars.
3 The lack of quality roads or test tracks on which to perform a repeatable and accurate test.
4 The time required for each test.
5 The subjectivity that humans bring into the rating system.
Typically less than a dozen axles can be tested by a major manufacturer in one shift due to all of the above complications. This low number is not statistically valid when it is considered that most manufacturers make thousands of axles each day. Even with all of the above problems, human testers in cars are the only widely accepted method of axle testing in the industry due to the lack of a better more reliable testing method. This lack of a scientific basis for rating axles and gear systems is made worse when the reader considers that modem cars are extremely quiet, and are evolving to become more quite. This market direction increases the pressure on axle and other gear manufacturers to make their products quieter. There is a need for a system that offers gear and axle manufacturers a repeatable, reliable, accurate and practical way of measuring gear noise in production or laboratory environments.
It is, therefore, an object of this invention to provide a system for testing an energy transfer system, such as a vehicle axle, quickly and inexpensively, and achieving repeatable results.
It is often desired in the testing of a differential gear train system to determine the qualitative characteristics of the engagement between the pinion and ring gears, excluding any gear engagement noises produced by the differential gear set. This would require both rotatory outputs to be driven at precisely the same speed, in order that the differential gear set not become active. Noise from the engagement between the members of the differential gear set will interfere with the qualitative determination of the noise being issued by the engagement between the pinion and ring gears, and is generally not otherwise sufficiently objectionable to warrant specific testing therefor, as it occurs usually only at slow vehicle speeds during turns.
The foregoing notwithstanding, it is expensive and complicated to test a differential axle system in a manner that excludes the noise of engagement of the members of the differential gear set, as precisely controlled loads are required at each axle output. During performance of such a test in a production environment, generally two people are required, one at each output, in order to achieve the testing throughput needed during production.
It is, therefore, another object of this invention to provide a testing arrangement and method for a differential axle system that permits rapid and effective testing of the engagement between the pinion and ring gears, without interference from the differential gear set.
In accordance with a further apparatus aspect of the invention, there is provided an arrangement for isolating a mechanical drive system for a vehicle while it is subjected to a testing process, the drive system being of the type having a rotatory input, at least two rotatory outputs, and a differential gear set arranged on a differential gear set shaft. In accordance with the invention, the arrangement is provided with a base for supporting the arrangement and the mechanical drive system. An isolation support supports the mechanical drive system whereby the mechanical drive system is translatable in at least one plane of freedom with respect to the base. In addition, a rotatory drive applies a rotatory drive force to the mechanical drive system, and a first drive coupler transmits a torque from the rotatory drive to the rotatory input of the mechanical drive system. A rotatory load is provided to apply a rotatory load force to the mechanical system. A second drive coupler transmits and receives torque from the rotatory load means to the differential gear set shaft of the mechanical drive system.
In one embodiment of the invention, the second drive coupler is provided with a load shaft having a load shaft termination for entering the mechanical drive system and engaging with the differential gear set shaft. The load shaft termination is provided with a fork-like termination distal from the rotatory load, the fork-like termination having first and second axially parallel protuberances, whereby the differential gear set shaft is accommodated therebetween during the engagement.
There is further provided an engagement arrangement for securing the mechanical drive system to the isolation support, the engagement arrangement having a first position with respect to the base wherein the mechanical drive system is installable on, and removable from, the isolation support, and a second position wherein the mechanical drive system is secured to the isolation support.
An engagement driver is coupled to the base and to the engagement arrangement for urging the engagement arrangement between the first and second positions, the engagement arrangement being coupled to the engagement driver when the engagement arrangement is in the first position, and isolated from the engagement driver when the engagement arrangement is in the second position.
In further embodiment of the invention, the mechanical drive system has forward and reverse directions of operation, and drive and coast modes of operation for each of the forward and reverse directions of operation. The mechanical drive system contains at least a pair of meshed elements, at least one of the pair of meshed elements being a gear having a plurality of gear teeth thereon, the gear teeth each having first and second gear tooth surfaces for communicating with the other element of the pair of meshed elements, a mechanical energy transfer communication between the pair of meshed elements being effected primarily via the respective first gear tooth surfaces during forward-drive and reverse-coast modes of operation, and primarily via the respective second gear tooth surfaces during forward-coast and reverse-drive modes of operation. In a practical embodiment of the invention, the pair of meshed elements is provided with a pinion gear and a ring gear.
A first acoustic sensor is arranged at a first location in the vicinity of the mechanical drive system for producing a first signal responsive substantially to a qualitative condition of the meshed engagement between the pinion gear and the ring gear. The qualitative condition of the meshed engagement between the pinion gear and the ring gear is responsive to a qualitative condition of respective first gear tooth surfaces of the pinion gear and the ring gear. A second acoustic sensor arranged at a second location in the vicinity of the mechanical drive system for producing a second signal responsive substantially to a qualitative condition of respective second gear tooth surfaces of the pinion gear and the ring gear.
In accordance with a further aspect of the invention, there is provided an arrangement for coupling a load to a mechanical drive system for a vehicle while the mechanical drive system is subjected to a testing process. The mechanical drive system is of the type having a rotatory input, at least two rotatory outputs, and a differential gear set arranged on a differential gear set shaft. In accordance with the invention, there is provided a rotatory load and a load shaft arranged to be coupled at a first end thereof to the rotatory load. The load shaft is adapted to be engaged at a second end thereof to the differential gear set shaft.
In one embodiment of this further aspect of the invention, the load shaft is provided with a fork-like termination distal from the rotatory load, the fork-like termination having first and second axially parallel protuberances, whereby the differential gear set shaft is accommodated therebetween during the engagement.
A rotatory drive applies a rotatory drive force to the rotatory input of the mechanical drive system. Additionally, a first drive coupler transmits and receives torque to and from the rotatory drive to the rotatory input of the mechanical drive system. In a preferred embodiment, the mechanical drive system contains a pinion gear and a ring gear, each having a plurality of gear teeth thereon, the gear teeth each having first and second gear tooth surfaces for communicating with the other of the pair of meshed elements. A mechanical energy transfer communication between the pair of meshed elements is effected primarily via the respective first gear tooth surfaces during forward-drive and reverse-coast modes of operation, and primarily via the respective second gear tooth surfaces during forward-coast and reverse-drive modes of operation.
In accordance with a method aspect of the invention, there is provided a method of testing a gear assembly of the type having a rotatory input, at least two rotatory outputs, and a differential gear set arranged on a differential gear set shaft. The method includes the steps of:
installing the gear assembly on a mounting arrangement that resiliently permits motion of the gear assembly in all directions, and that has a resilient frequency characteristic that excludes all natural frequencies of the gear assembly;
applying a torque at the input of the gear assembly, whereby the gear assembly is rotatably operated;
applying a load at the differential gear set shaft of the gear assembly; and
sensing a predetermined operating characteristic of the gear assembly.
In one embodiment of this method aspect of the invention, there is provided the further step of detecting acoustic energy issued by the differential gear set shaft of the gear assembly.
In further embodiments there are selectably provided the steps of:
determining a qualitative condition of a pinion and ring gear assembly in the gear assembly under test;
detecting acoustic energy is provided with the further step of detecting vibratory displacement energy issued by the gear assembly; and
monitoring a variation in temperature over time of the gear assembly.
In accordance with a further apparatus aspect of the invention, there is provided a torque sensor interposed between the rotatory drive and the mechanical drive system. The torque sensor produces a signal that is responsive to a torque applied by the rotatory drive to the mechanical drive system. Preferably, the torque sensor is arranged to produce a static torque signal that is responsive to the magnitude of torque required to initiate rotatory motion in the mechanical drive system. Additionally, the torque sensor produces a dynamic torque signal that is responsive to the magnitude of torque required to maintain rotatory motion in the mechanical drive system. The torque sensor is provided with a torque-transmitting element that has a predetermined deformation characteristic. The torque-transmitting element becomes deformed in response to the torque applied by the rotatory drive system to the mechanical drive system. A strain sensor is coupled to the torque-transmitting element to produce a strain signal that is responsive to the predetermined deformation characteristic of the torque-transmitting element, and consequently, the applied torque.
In a further embodiment, there is provided a sensor that is arranged to communicate with the mechanical drive system for producing an information signal that is responsive to an operating characteristic of the mechanical drive system in response to the rotatory drive force. A further sensor communicates with the mechanical drive system for producing a further information signal that is responsive to a further operating characteristic of the mechanical drive system in response to the rotatory drive force. The operating characteristic and the further operating characteristic of the mechanical drive system correspond, in a highly advantageous embodiment of the invention, to drive and coast operating modes in response to a direction of torque of the rotatory drive force. As previously stated, the sensor in one embodiment is arranged to be translatable between a first position distal from the mechanical drive system, and a second position where the sensor communicates with the mechanical drive system.
In this further apparatus aspect, the sensor may be provided with a microphone that is responsive to an acoustic energy issued by the mechanical drive system in response to the rotatory drive force. In another embodiment, the sensor is provided with an accelerometer, or with a velocity sensor. In other embodiments, the sensor is installed on the engagement arrangement, and is translatable therewith between the respective first and second positions.
In some arrangements, the sensor is a non-contact sensor that produces a displacement signal that is responsive to displacement of the mechanical drive system in response to the rotatory drive force. Such a non-contact sensor may be a laser sensor for communicating optically with the mechanical drive system. Additionally, the non-contact sensor produces a thermal signal that is responsive to a temperature of the mechanical drive system, such as an infrared sensor that communicates optically with the mechanical drive system. As previously noted, in one specific illustrative embodiment of the invention, the thermal sensor means has a directional characteristic and is directed to a predetermined region of the energy transfer system for determining a rate of change of temperature of the predetermined region with respect to time. In this embodiment, there is provided an acoustic sensor sensitivity control arrangement that is responsive to the thermal sensor for varying the amplitude of a noise signal in response to temperature. The variation of the amplitude of the noise signal with respect to temperature is performed in accordance with a non-linear amplitude-temperature relationship. The variation in temperature over time is useful to indicate low lubricant level, low lubricant quality, or low bearing quality.
In a further embodiment, the isolation support is provided with a resilient support element for supporting the mechanical drive system, and is provided with a resilience frequency characteristic that excludes a natural frequency of the mechanical drive system. Additionally, the resilience frequency characteristic of the resilient support element excludes a natural frequency of the drive coupler.
In a mechanical embodiment of the invention, there is additionally provided a rotatory load for applying a rotatory load to the mechanical drive system, and a load coupler for coupling the rotatory load to the rotatory input of the mechanical drive system. The mechanical drive system is in the form of a drive-transmitting component for a motor vehicle. In such an embodiment, the rotatory load applies a controllable rotatory load thereto to simulate a plurality of vehicle operating conditions. These include, for example, gear drive and coast conditions, as well as a gear float condition.
The engagement driver is provided, in one embodiment, with a linear actuator that has a first end coupled to the base, and a second end coupled to the engagement arrangement. An engagement coupler is interposed between the engagement arrangement and the engagement driver. The engagement coupler is provided with a support portion installed on the isolation support, and first and second engagement arms pivotally coupled to the support portion. Additionally, first and second articulated members are coupled at a pivot point to one another and to the linear actuator. They further are pivotally coupled at distal ends thereof to respective ones of the first and second engagement arms, whereby the linear actuator urges the pivot point along a linear path to a latching position beyond where the first and second articulated members are axially parallel. As previously noted, a resilient biasing arrangement that is installed on at least one of the first and second engagement arms applies a resilient biasing force to the energy transfer system. The resilient biasing arrangement applies a resilient biasing force that maintains the engagement arrangement in the second position.
In accordance with a further method aspect of the invention, there is provided a method of testing a gear assembly of the type having an input and an output. The method includes the steps of:
installing the gear assembly on a mounting arrangement that resiliently permits motion of the gear assembly in all directions, and that has a resilient frequency characteristic that excludes all natural frequencies of the gear assembly;
applying a torque at the input of the gear assembly, whereby the gear assembly is rotatably operated;
to applying a load at the output of the gear assembly; and
sensing a predetermined operating characteristic of the gear assembly.
In one embodiment of this method aspect of the invention, the step of sensing is provided with the step of detecting acoustic energy issued by the gear assembly. Also, the step of detecting acoustic energy issued by the gear assembly is provided with the step of placing a microphone n the vicinity of the gear assembly.
In a further embodiment, the step of sensing is provided with the step of detecting vibratory displacement energy issued by the gear assembly. The step of detecting vibratory displacement energy issued by the gear assembly is provided with the further step of effecting communication between an accelerometer and the gear assembly, and the step of detecting vibratory displacement energy issued by the gear assembly is provided with the further step of effecting communication between a velocity sensor and the gear assembly.
After performing the step installing there is further provided the step of clamping the gear assembly to the mounting arrangement. In an embodiment where the mounting arrangement is installed on a reference base portion, the step of clamping is performed in response to the further step of applying a clamping actuation force to a clamping arrangement with respect to the reference base portion. A clamping actuation force is applied, and the gear arrangement is enabled to move freely independent of the reference base portion.
In a further embodiment, the step of applying a clamping force is provided with the further step of applying a resilient clamping force to the gear assembly. This step may, in certain embodiments, include the further step of monitoring a predetermined dimension of the gear assembly in response to the step of clamping. This is accomplished by use of a sensor that measures distance traveled.
Sensing is effected by monitoring a first sensor that receives acoustic energy that is responsive to a qualitative condition of the gear assembly in a drive mode of operation. When the drive mode of operation is in a first direction of operation, the qualitative condition of the gear assembly in the drive mode of operation includes a qualitative condition of a first surface of the teeth of the gear assembly. Also when drive mode of operation is in a first direction of operation, the qualitative condition of the gear assembly in the drive mode of operation includes a qualitative condition of a profile of a gear of the gear assembly, and a qualitative condition of the eccentricity of a gear of the gear assembly. Additionally, the qualitative condition of the gear assembly in the drive mode of operation includes a qualitative condition of the angular orientation of the gears of the gear assembly. In still further embodiments of the method aspect of the invention, wherein the drive mode of operation is in a first direction of operation, the qualitative condition of the gear assembly in the drive mode of operation includes a qualitative condition of a plurality of moving components of the gear assembly.
In a further embodiment of the invention, the step of sensing is provided with the further step of monitoring a second sensor that receives acoustic energy that is responsive to a qualitative condition of the gear assembly in a coast mode of operation. The coast mode of operation includes a qualitative condition of a second surface of the teeth of the gear assembly. When the coast mode of operation is in a first direction of operation, the qualitative condition of the gear assembly in the coast mode of operation includes a qualitative condition of a profile of a gear of the gear assembly. Additionally, the qualitative condition of the gear assembly in the coast mode of operation includes a qualitative condition of the eccentricity of a gear of the gear assembly, as well as the angular  orientation of the gears of the gear assembly. In further embodiments, the coast mode of operation includes a qualitative condition of a plurality of moving components of the gear assembly.
In accordance with a further embodiment of this method aspect of the invention, the drive and coast modes of operation are cyclical over a period that is shorter than a cycle period of the input of the gear assembly. Conversely, the period can be longer than a cycle period of the input of the gear assembly. This will depend, to an extent, upon the operating ratios within the system under test.
In an advantageous embodiment, the first and second sensors are disposed at respective locations that are distal from each other, with the gear assembly interposed therebetween. This enables distinguishing between operating modalities of the system under test, as well as facilitating analysis of operating characteristics of the system under test that have directional components.
In accordance with a clamping aspect of the present invention, there is provided an arrangement for clamping a workpiece to a resilient support element. In this aspect of the invention, there is provided a support base installed on the resilient support element. First and second clamping arms are each coupled to the support base by a respective first pivot coupling and arranged to rotate pivotally about the respective first pivot couplings between respective clamped and released counter rotational positions. Each of the first and second clamping arms is further provided with a respective second pivot coupling. First and second links are included in the combination, each having a respective central axis between a respective first pivot coupling where the first and second links are pivotally coupled to one another, and respective second pivot couplings where each of the first and second links is coupled to a second pivot coupling of a respectively associated one of the first and second clamping arms. A drive arrangement urges the first and second links from a first angulated link position corresponding to the released counter rotational position of the first and second clamping arms to a second angulated link position on the other side of a coaxial position of the first and second links, the second angulated link position corresponding to the clamped counter rotational position of the first and second clamping arms. Also, a drive coupler the is arranged to couple drive arrangement to at least one of the first and second links whereby the drive arrangement is decoupled from the first and second links when the links are in the second angulated link position.
In one embodiment of the clamping aspect of the invention, the drive coupler is coupled to the first pivot couplings of the first and second links. In an embodiment where the workpiece has a vibratory displacement characteristic, the clamping arrangement is substantially freely displaceable in response to the vibratory displacement characteristic of the workpiece while the first and second links are in the second angulated link position.
A sensor is installed on at least one of the first and second clamping arms for detecting a predetermined operating characteristic of the workpiece. The may detect a displacement of the workpiece, or an acoustical energy issued by the workpiece.
In an embodiment where the workpiece is a gear assembly having a rotatory input and an output, there is additionally provided a rotatory drive for applying a torque at the rotatory input of the gear assembly. Also, a drive coupler couples the rotatory drive to the rotatory input of the gear assembly. The drive coupler is arranged to provide substantially only torque to the gear assembly at its rotatory input, without any substantial axial loading, and to attenuate the propagation of acoustic energy from the rotatory drive arrangement. A load is coupled to the output of the gear assembly, the load being arranged to simulate an actual operating condition of the gear assembly.
In accordance with a drive coupling aspect of the invention, substantially exclusively torque is transmitted from a drive arrangement to a gear assembly under test. The drive coupling arrangement includes a first coupler portion attached to the drive coupling arrangement, the coupler having a polygonal cross-sectional configuration that extends continuously over a predetermined length of axis. The polygonal cross-sectional configuration has a plurality of substantially planar surfaces that extend parallel to the predetermined length of axis. A second coupler portion is provided and has an internal cross-sectional configuration that accommodates the polygonal cross-sectional configuration of said first coupler portion. The second coupler portion is provided with a plurality of engagement portions that communicate exclusively with a predetermined number of the substantially planar surfaces of said first coupler portion. The first and second coupler portions are axially translatable along said first coupler portion for a portion of the predetermined length of axis. Therefore, the torque is transmitted between the first and second coupler portions without exerting an axial load.
In one embodiment of this drive coupling aspect of the invention, the polygonal cross-sectional configuration corresponds to a hexagon. Also, the second coupler portion has three engagement portions that engage three respective planar surfaces of the first coupler portion.
In accordance with a further method aspect of the invention, there is provided a method of signal analysis for processing information from a gear system under test. This further method aspect includes the steps of:
driving the gear system under test by application of a rotatory input;
producing a first signal responsive to the torque applied to the gear system under test;
producing first digital data responsive to a first correlation between the first signal and time;
measuring peaks in said first digital data to determine whether the peaks exceeds a predetermined threshold magnitude; and
first subjecting those of the peaks that exceed the predetermined threshold magnitude to harmonic analysis.
In a specific illustrative embodiment of the invention of this further method aspect, there is provided the further step of comparing the result of the harmonic analysis of the step of first subjecting against gear tooth harmonics to determine whether the peaks constitute an anomaly. Such an anomaly is a bump or a nick on a tooth of the gear system under test.
In a highly advantageous embodiment of the invention wherein improved results are obtained, there are provided the further steps of:
producing a second signal responsive to a noise produced by the gear system under test in response to the step of driving;
producing a second digital data responsive to a second correlation between the second signal and time;
identifying peaks in the second digital data that are simultaneous with peaks in said first digital data;
measuring the simultaneous peaks in the second digital data to determine whether they exceed a second predetermined threshold magnitude; and
second subjecting those of the simultaneous peaks in the second digital data that exceed the second predetermined threshold magnitude to harmonic analysis.
As is the case in the embodiment where only the torque signal is subjected to harmonic analysis, there is additionally provided in this embodiment the further step of comparing the result of the harmonic analysis of the steps of first subjecting and second subjecting against gear tooth harmonics to determine whether the simultaneous peaks constitute an anomaly. Thus, in this embodiment, the torque and the noise signals are subjected to harmonic analysis. It is desired in an embodiment of the invention that is used to test gear systems, to determine whether the anomaly is a bump or a nick on a tooth of the gear system under test. In a further step of calculating, the severity of the anomaly determined in the step of comparing is determined.
In a still further embodiment of this method aspect, there are provided the further steps of:
establishing predetermined harmonic criteria; and
determining whether the results of the analysis in the step of subjecting conforms to the predetermined harmonic criterial of the step of establishing.
In accordance with a still further method aspect of the invention, there is provided a method of signal analysis for processing information from a gear system under test for determining the presence of bumps or nicks therein. In this still further method aspect, there are provided the steps of:
driving the gear system under test by application of a rotatory input;
producing a first signal responsive to the torque applied the gear system under test;
producing a second signal responsive to a noise produced by the gear system under test in response to the step of driving;
producing first digital data responsive to a first correlation between the first signal and time;
producing a second digital data responsive to a second correlation between the second signal and time;
identifying simultaneous peaks in the first and second digital data;
measuring the simultaneous peaks in the first and second digital data to determine whether they exceed a predetermined threshold magnitude; and
subjecting those of the simultaneous peaks that exceed the predetermined threshold magnitude to harmonic analysis.
In one embodiment of this method aspect, there is provided the further step of comparing the result of the harmonic analysis of the step of subjecting against gear tooth harmonics to determine whether the simultaneous peaks constitute an anomaly. In a further embodiment, there is provided the further step of calculating the severity of the anomaly of the step of comparing.